With the ubiquitous nature and ever increasing popularity of the Internet and with the use of the Internet to support, for example, telephony services, known, as IP telephony services or voice over IP (VOIP), there is a need to provide high availability network equipment to support such voice services. A high availability service aims to provide service continuity in that the telephony service is available both before and after a system failure. A break in the support of the voice service of, for example, 300 milliseconds will be perceivable by a human and will degrade the quality of the service of the link. These high availability systems are implemented using gatekeepers, as is known within the art.
In the case of failure of the gatekeeper typically all calls are torn down. This results in all parties being unable to communicate without prior notice. Clearly such an abrupt disruption is undesirable
Suitably, it is known within the art to provide fault tolerant H.323 gatekeepers in which a gatekeeper function is supported using active and stand-by hosts. The active gatekeeper manages the call set-up, tear-down and other telephony functions for all associated calls. The stand-by gatekeeper is ready to assume the role of active gatekeeper in the event of a fault with the current active gatekeeper.
To implement call preservation using a connection-oriented protocol would require providing a highly available protocol stack. Conventional wisdom directs one skilled in the art, when contemplating implementing a highly available system, to design and develop software that preserves a protocol stack. Providing such a highly available protocol stack, which includes connection layer information, such as IP and TCP layers, and signalling layers such as H.323 or Q.931 and other application layers represents an enormous design and development overhead during the production of the system. Additionally, the amount of system resources required to preserve such a protocol stack would reduce the performance of the system since a significant amount of memory, data processing and CPU power would be consumed during any such protocol stack preservation.
It is an object of the present invention at least to mitigate some of the problems of the prior art.